Self-charging accumulator



Jung 23, 1959 J. R. JER-OMSON, JR 2,891,554 SELF-CHARGING ACCUMULATOR Filed Aug. .3, 1956 United States Patent 1 SELF-CHARGING ACCUMULATOR James R. Jeromson, Jr., Willoughby Hills, Ohio, assignor to Thompson Products, Inc Cleveland, Ohio, a corporation of Ohio Application August 3, 1956, Serial No. 601,893

7 Claims. (Cl. 13831) The present invention is directed to a self-charging accumulator used as an energy storage device in a hydraulic system.

In many hydraulic systems, such as the hydraulic sys terns used to actuate various accessories such for example as power steering and power brake systems in automo biles, the hydraulic pressure in the line serving the acces sories must be maintained between prescribed limits. In normal operation, however, a sudden surge may exceed the capacity of the pump during those periods. To compensate for these periods of excessive requirement, it is advisable to include an accumulator in the hydraulic sys term which supplies the hydraulic feed line with an addi tional source of hydraulic fluid under pressure. Nor mally, such hydraulic accumulators are fed from the pump and build up their pressure during the time that the hydraulic system is not loaded by the hydraulically operated accessories. In the normal accumulator, the fluid under pressure operates a displacement mechanism to build up a substantial pressure of a compressible fluid such as air in a vessel and uses the compressed fluid as the medium for supplying the stored hydraulic fluid back into the hydraulic feed line during periods of high demand.

Accumulators of the type described cannot, as a practical matter, be made completely airtight and for that reason the normal leakage which occurs through the accumulator frequently causes erratic operation of the accumulator during its discharge. To overcome this defect, the present invention provides a self-charging accumulator in which the air in the compressed air chamber is periodically replenished to make up for any loss of air due to leakage.

An object of the present invention is to provide an improved self-charging accumulator in which the losses due to leakage of air are replaced during normal operation of the accumulator.

Another object of the invention is to provide an automatically opera'ble accumulator including an auxiliary air compressing system which supplies air under pressure to the main air compressing system contained within the accumulator.

Another object of the present invention is to provide a self-charging accumulator which is relatively simple in construction and inexpensive to manufacture.

A further description of the present invention will be made in conjunction with the attached sheet of drawings which illustrate a preferred embodiment thereof.

In the drawings:

Figure 1 is a view in cross section, and partly in elevation, of an accumulator embodying the principles of the present invention, with various portions thereof broken away to illustrate the mechanism more completely; and

Figure 2 is a cross-sectional view taken substantially along the line Ii-II of Figure 1.

As shown on the drawings: I

In Figure 1, reference numeral 10 indicates generally the accumulator of the present invention which includes a hollow cylindrical casing 11 having its forward end 2,891,554 Patented June 23, 1959 lCe closed by means of a closure plate 12 and its opposite end closed by means of a closure plate 13. As illustrated in Figure 1, the casing 11 is tightly received against shoulders 12a and 13a provided in the closure plates 12 and 13, respectively, and may be suitably secured thereto.

The closure plates 12 and 13 are also provided with additional axially projecting shoulders 12!) and 13b concentrically radially inwardly of the shoulders 12a and 13a which serve to locate a relatively large diameter cylinder sleeve 14 in casing 11. The cylinder sleeve 14 is spaced concentrically inwardly from the casing 11 and is of generally coextensive longitudinal size thereby to provide an annular air chamber 16 which communicates with the main air space 18 in the cylinder sleeve 14 through one or more apertures or ports 17 formed in the cylinder sleeve 14, and thereby prevent the possibility of applying non-uniform pressures at opposite sides of the walls of the cylinder sleeve 14.

A piston generally indicated at 19 is arranged to reciprocate Within the cylinder sleeve 14 and to compress the air in the air space 18 during such reciprocation. The piston 19 includes a piston head 21 carrying an O-type seal ring 22 for sliding engagement with the walls of the cylinder sleeve 14. The piston head 20 is characterized by a hydraulic pressure face 20a on one side thereof subject to pressure from the output line of the pump or to the working pressure of the hydraulic system as supplied by means of a conduit 23 extending through the closure plate. 0n the opposite side of the piston head 20 is an air cushion pressure face 20b subject to the air pressure developed in the main air space 18.

According to the present invention, self-charging means are integrated with the piston 19 to replenish air to the space 18.

A second cylinder sleeve 26 is disposed axially of the cylinder sleeve 14 and has one end bottomed securely in an annular groove 13c provided in the closure plate 13. The auxiliary cylinder sleeve 26 receives an auxiliary piston 27 which is operatively associated and preferably integral with the piston head 21. A pair of spaced seal rings 28 and 29 are provided longitudinally along the length of the piston 27 to prevent fluid leakage along the sides of the piston.

The cylinder sleeve 26 also receives a check valve assembly at one end including a hollow cylinder 31 in tight frictional engagement with the inside walls of the sleeve 26. The cylinder 31 may be secured to the cylinder sleeve 26 or to the closure plate 13, or both, by means of brazing or the like, if desired. The cylinder 31 has an axially extending air passageway 32 which is in open communication with a conduit 33 supplying atmospheric air to the passageway 32. The flow of air from the passageway 32 to the air chamber 34 existing within the cylinder sleeve 26 is controlled by means of a pressure responsive valve such as a poppet valve 36 having a valve seat 37 arranged to be received on a valve seating face 38 provided in the cylinder 31.

The valve 36 has a valve stem 39 slidably received within a valve guide 41. A plurality of spaced longitudinal passages 42 are provided to direct the air flow trom the passageway 32 through the valve stem guide 41.

A relatively light spring 43 has one end bottomed against the valve stem guide 41 and its opposite end received against .a valve retainer or collar 45 disposed at one end of the stem 39. Thus when pressure in the air chamber 34 is reduced the valve 36 automatically opens to admit more air. V

The auxiliary piston 27 is provided with an axially extending passageway 44. A check valve which may take the form of a ball 46 normally urged into seated relation against an orifice 47 by the action of a spring 48 controls the flow of air pressurized in the auxiliary air chamber 34 by movement of the piston 27 into the axial passageway 44. The air at increased pressure thus introduced into the axial passageway 44 is ultimately charged into the main air space 18 of the cylinder sleeve 14 through another pressure responsive valve including a radially extending opening having a valve seat 49 communicating with the axial passage 44, and a ball 51 which is normally urged into seated relation against the seat 49 by the action of a spring 52. The latter spring is somewhat stifier than the spring 48, so that an air pressure may be built up in the axial passage 44 before the ball 51 is unseated.

In order to prevent an excessive buildup of pressure in the air space 18, a relief valve is provided in the closure plate 13, the valve consisting of a ball 53 being urged into its closed position against an orifice 54 communicating with the air space 13 by the action of a spring 56. In the event that the pressure in the air space 18 becomes excessive, the pressure will be sutlicient to unseat the ball 53 from the orifice 54 and permit discharge of the accumulated air to the atmosphere through a vent 57.

During the periods of low demand, the accumulator receives the hydraulic fluid such as oil under pressure from the inlet conduit 23. The fluid pressure causes the main piston 19 to move to the right, as viewed in Figure 1, thereby compressing air within the main air space 18. At the same time, the auxiliary piston 27 is moved inwardly of the cylinder sleeve 26, thereby compressing air in the air space 34 associated with the cylinder sleeve 26. Toward the end of the stroke, the pressure built up in the air space 34 causes the ball 46 to be unseated, permitting the flow of air from the air space 34 through the orifice 47 and into the axially extending passage 44 of the piston 27. After several strokes, or cycles, the pressure in the axially extending passage 44 will be suflicient to cause ball 51 to be unseated from the radially extending passage 49 and the air will be delivered into the main air space 18 of the cylinder. This discharge of air occurs when the pistons 21 and 22 are at their extreme left position, as viewed in Figure 1, that is, when the air pressure in the main air space 18 is at its minimum value. Any air loss due to leakage is thereby automatically replaced.

As the hydraulic fluid is supplied from the accumulator, the main piston 21 moves to the left, as viewed in Figure 1, and so carries the auxiliary piston 27 along with it. At this time, the resultant reduction in pressure in the air space 34 of the cylinder sleeve 26 is sufficient to overcome the bias provided by the relatively light spring 43 on the poppet valve and outside air is thereby admitted from the inlet 33 into the air space 34.

Thus, each time the accumulator operates, additional amounts of air are drawn into the auxiliary air compressing system and vented to the main air compressing system when the accumulator discharges its previously stored hydraulic fluid. In the event that the air pressure in the chamber should exceed a desired value, the relief valve 53 opens to the atmosphere and relieves the pressure.

From the foregoing, it will be apparent that the selfcharging accumulator of the present invention provides a self-regulating system for maintaining a proper supply of air into the accumulator. It will also be evident that various modifications can be made to the described embodiment without departing from the scope of the present invention.

I claim as my invention:

1. self-charging accumulator comprising a cylinder, a main piston having a piston head reciprocable in said cylinder in response to pressure variation on pposite sides of said piston head to compress air contained in said cylinder, means for introducing a fluid under pressure against said piston head, a cylinder sleeve mounted in said cylinder, an auxiliary piston movable with said main piston and reciprocable in said cylinder sleeve to compress air in said cylinder sleeve, means for periodically admitting air into the cylinder sleeve, a pressure sensitive means in said auxiliary piston actuated by the air pressure in said cylinder sleeve, passage means within said auxiliary piston receiving the air flow through said pressure sensitive means, and discharge means in said auxiliary piston communicating with said passage means and arranged to discharge air from said passage means into the air space in said cylinder.

2. A self-charging accumulator comprising a cylinder, a main piston having a piston head reciprocable in said cylinder in response to pressure variations on opposite sides of said piston head to compress air contained in said cylinder, means for introducing a fluid under pressure against said piston head, a cylinder sleeve mounted in said cylinder, an auxiliary piston movable with said main piston and reciprocable in said cylinder sleeve to compress air in said cylinder sleeve, means for periodically admitting air into the cylinder sleeve, a pressure sensitive means in said auxiliary piston actuated by the air pressure in said cylinder sleeve, axially extending passage means within said auxiliary piston receiving the air flow through said pressure sensitive means, and radially extending discharge means in said auxiliary piston communicating with said passage means and arranged to discharge air from said passage means into the air space in said cylinder.

3. A self-charging accumulator comprising a cylinder, a headed main piston reciprocable in said cylinder, means communicating one side of the piston head to a source of pressured fluid, said main piston being arranged to compress the air in said cylinder upon displacement of said main piston into said cylinder by the pressure of said fluid, a cylinder sleeve secured axially of said cylinder, an auxiliary piston coaxial with said main piston and movable therewith, said auxiliary piston extending into said cylinder sleeve and being arranged to compress air in said cylinder sleeve during its stroke therein, said auxiliary piston having an axially extending passageway therein and a radially extending passageway communicating said axially extending passageway with the air space in said cylinder, a pressure responsive check valve disposed in said axially extending passageway, a pressure responsive valve disposed in said radially extending passageway, an air inlet extending into said cylinder and arranged to introduce air into said cylinder sleeve, and a pressure responsive check valve controlling the air flow from said inlet into said cylinder sleeve.

4. A self-charging accumulator comprising a cylinder, a headed main piston reciprocable in said cylinder, means communicating one side of the piston head to a source of pressured fluid, said main piston being arranged to compress the air in said cylinder upon displacement of said main piston into said cylinder by the pressure of said fluid, a cylinder sleeve secured axially of said cylinder, an auxiliary piston integral with and coaxial with said main piston, said auxiliary piston extending into said cylinder sleeve and being arranged to compress air in said cylinder sleeve during its stroke therein, said auxiliary piston having an axially extending passageway therein and a radially extending passageway communicating said axially extending passageway with the air space in said cylinder, a pressure responsive check valve disposed in said axially extending passageway, a pressure responsive check valve disposed in said radially extending passageway, an air inlet extending into said cylinder and arranged to introduce air into said cylinder sleeve, and a pressure responsive check valve controlling the air flow from said inlet into said cylinder sleeve.

5. A self-charging accumulator comprising a cylinder, a main piston reciprocable in said cylinder to compress air within an air space in said cylinder, means for introducing a fluid under pressure against said main piston to cause displacement of said main piston within said cylinder, a cylinder sleeve secured axially of said cylinder, an axially bored auxiliary piston carried by said main piston and received in sliding relation Within said cylinder sleeve to compress air within said cylinder sleeve, an inlet arranged to introduce air periodically into said cylinder sleeve, a pressure responsive valve means controlling the introduction of air from said inlet to said cylinder sleeve, a pressure responsive valve closing one end of said bore in said auxiliary piston for controlling the flow of air into said axial bore, and a pressure responsive valve arranged to deliver air from said axial bore into the air space in said cylinder.

6. In an accumulator, a cylinder having a hydraulic fluid inlet at one end and being closed at the opposite end, a piston in said cylinder having a hydraulic pressure face on one side of said piston and an air pressure face on the opposite side of said piston, said piston being movable in said cylinder toward said closed end against an air cushion upon being hydraulically loaded, and pulsating compressor means operatively connected to said piston and operable in unison therewith and having an air inlet communicating with the atmosphere and an air outlet discharging into the closed end of said cylinder, thereby to replenish air lost from the air cushion, said pulsating compressor means comprising an auxiliary piston extending axially from said air pressure face into said cylinder, an auxiliary cylinder carried inside of said main cylinder and receiving said auxiliary piston, and valve controlled passage means communicating said auxiliary cylinder with the air inlet and the air outlet.

7. In an accumulator, a cylinder having a hydraulic fluid inlet at one end and being closed at the opposite end, a piston in said cylinder having a hydraulic pressure face on one side of said piston and an air pressure face on the opposite side of said piston, said piston being movable in said cylinder toward said closed end against an air cushion upon being hydraulically loaded, and pulsating compressor means operatively connected to said piston and operable in unison therewith and having an air inlet communicating with the atmosphere and an air outlet discharging into the closed end of said cylinder, thereby to replenish air lost from the air cushion, said pulsating compressor means comprising an auxiliary piston extending axially from said air pressure face into said cylinder, an auxiliary cylinder carried inside of said main cylinder and receiving said auxiliary piston, and valve controlled passage means communicating said auxiliary cylinder with the air inlet and the air outlet, at least a portion of said valve controlled passage means being formed in and extending through the interior of said auxiliary piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,905,133 Bishop et a1 Apr. 25, 1933 2,605,716 Huber Aug. 5, 1952 

